Recording covers and trying to exactly duplicate the original sounds will help teach you a lot about your equipment, and help you realize how to duplicate what's in your head.
You should check out an album called "Faithful' by Todd Rundgren. One side was originals, and the other was note for note reproductions of things like Strawberry Fields Forever, and Good Vibrations. He's had moderate success as an artist, but is a hugely successful producer, best known for producing Meatloaf's Bat Out of Hell.
I had to ask though, because I just finished a session for a band that recorded cover's of Blink and MXPX. I can think of many better ways to spend the money, so thanks to their foolishness, I will.
Jeff